Equilibrium and kinetic studies of the stannate(IV)-polyol reaction

The stability constants of 1:1 stannate(IV)-polyol complexes in aqueous media have been determined using a conductimetric technique. The constants are fairly large, and lie in the range 5.3-123.0 for the ten ligands investigated. These values were subsequently used in conjunction with kinetic data to postulate a mechanism involving the species Sn(OH)5- as intermediate in the formation of the chelates. The stannate(IV)-polyol reaction, though taking place at higher pH values, is acid-catalysed and follows first-order kinetics in the oxyanion, but at large ligand-oxyanion mole ratios the reaction exhibits zero-order rate dependence on the polyol. These features taken together are consistent with a unimolecular nucleophilic substitution on the oxyanion. KEY WORDS: Hexahydroxystannate(IV), Polyol, Stability constants, Conductimetric method, Mechanism Bull. Chem. Soc. Ethiop. 2010, 24(3), 447-456.